SPOILAGE-OF-FISH.pdf

FISH SPOILAGE ELLAN JOY T. MANDARIO DEPARTMENT OF FISH PROCESSING AND MARINE BIOLOGY COLLEGE OF FISHERIES-MINDANAO STATE UNIVERSITY GENSAN  WHY FISH SPOILS? SPOILAGE - is a result of a series of complicated changes brought about mainly by enzymatic and bacterial action SHELFLIFE- time when the p...

FISH SPOILAGE ELLAN JOY T. MANDARIO DEPARTMENT OF FISH PROCESSING AND MARINE BIOLOGY COLLEGE OF FISHERIES-MINDANAO STATE UNIVERSITY GENSAN  WHY FISH SPOILS? SPOILAGE - is a result of a series of complicated changes brought about mainly by enzymatic and bacterial action SHELFLIFE- time when the product is perceived as being di erent by certain amount ff AGENTS AGENTS OF SPOILAGE AGENTS OF SPOILAGE SPOILAGE ENZYMES - which is either found in the sh tissues or elaborated by microorganisms during growth. *ENDOGENOUS - inherent in the organisms AUTOLYSIS - is the self-breakdown or self- digestion that results tot he weakening, softening and discoloration of sh tissues fi fi AGENTS AGENTS OF SPOILAGE AGENTS OF SPOILAGE SPOILAGE CHEMICAL REACTION - that are not mainly due to enzymes , such as lipid oxidation. *LIPID AUTOLYSIS - enzymatic hydrolysis of free fatty acid and glycerol *AUTOOXIDATION - reaction of unsaturated lipid with oxygen e.g. malonaldehydes, peroxides *RANCIDITY - spoilage of oils and fats  LIPID OXIDATION Usually occurs during the last stage of sh spoilage. It leads tot he hydrolysis and oxidation of fat which causes rancidity and results to the formation of hydroperoxides, peroxides or free fatty acids (FFA) and malonaldehydes This is due to the large amount of polyunsaturated fatty acid moieties found in sh lipids. In fact this is a major cause of spoilage of frozen sh. fi fi fi AGENTS OF SPOILAGE AGENTS OF SPOILAGE AGENTS OF SPOILAGE MICROORGANISMS - which may be present in the gills or on the surface (originating from the water from which sh is taken or maybe picked up during post-harvest handling) *the quality if water where the sh is caught determines the amount of organisms fi fi AGENTS OF SPOILAGE STAGES OF BACTERIAL SPOILAGE LIVE FISH- sterile esh; biochemically FFESHLY CAUGHT FISH - muscles relaxed, rm, FISH RIGOR MORTIS - muscles stiff, tough, AUTOLYSED FISH MEAT - partly hydrolysed protein; soft meat; series of enzymatic and bacterial BACTERIAL DECOMPOSITION - bacterial load increase exponentially LIPID OXIDATION - oxidation products fl fi  TYPES OF BACTERIA PSYCHROPHILIC BACTERIA - loves low temperature *Alteromonas sp., Achromobacter sp., Flavobacter sp. * Shrimp on ice: Alteromonas sp., Moraxella sp., Vibirio parahaemolyticus, Bacillus sp. MESOPHILIC BACTERIA - loves ambient temperature THERMOPHILIC BACTERIA - loves high temperature *Fish at 35℃-55℃: Bacillus sp., Micrococcus sp. CHEMICAL CHANGES ASSOCIATED WITH BACTERIAL SPOILAGE DEGRADATION OF TRIMETHYLAMINE (TMA) only marine species has TMAO (trimethylamine oxide) - use for osmoregulation Turbot - the only freshwater sh that has TMAO Determined by measuring TMA-N content of sh by Conway’s Microdi usion Method F O R M AT I O N O F D I M E T H Y L A M I N E ( D M A ) & FORMALDEHYDE (FA) dimethylamine and formaldehyde is mainly attributed to the action of endogenous TMAO aldolase enzyme. ff fi fi  CHEMICAL CHANGES ASSOCIATED WITH BACTERIAL SPOILAGE TOTAL VOLATILE BASE-NITROGEN (TVB-N) Refers to the total amount of a variety of N- containing substances produced during storage of sh A general term which includes the measurement of tirmethylamine (TMA), dimethlyamine (DMA), ammonia and other volatile basic nitrogenous compounds One of the most widely used measurements of seafood quality fi  CHEMICAL CHANGES ASSOCIATED WITH BACTERIAL SPOILAGE HISTAMINE FORMATION A biogenic amine considered as a relevant freshness or quality index in scombroid species Formation via enzymatic activity associated with bacteria Bacterial histidine decarboxylase-sensitive to temperature higher than room temperature *BIOGENIC AMINES - products of decarboxylation of certain types of amino acids  CHEMICAL CHANGES ASSOCIATED WITH BACTERIAL SPOILAGE HISTAMINE - has been associated with s c o m b ro i d p o i s o n i n g caused by eating tuna, mackerel and mahi-mahi  BIOGENIC AMINES HISTAMINE - product of decarboxylation of histidine PUTRESCINE - product of decarboxylation of ornithine CADAVERINE - product of decarboxylation of lysine TYRAMINE - product of decarboxylation of tyrosine  CHANGES OF FISH AFTER DEATH CHANGE IN COLOUR - the colour of the gills, skin and esh starts to fade after death fl  CHANGES OF FISH AFTER DEATH RIGOR MORTIS - this occurs a few hours after the death of the sh. Fish in this state are characterized by the sti ness of the body due to the formation of lactic acid caused by bacteria fi ff CHANGES OF FISH AFTER DEATH AUTOLYSIS - self digestion in the muscle tissue of the sh by enzymes due to continuous digestion even in death. fi CHANGES OF FISH AFTER DEATH Death of sh The nervous and hormonal control of the muscle ceases Hormones like steroids, protein, etc. from the blood streams stops Control of enzymes ceases to a large extend Autolysis sets in fi CHANGES OF FISH AFTER DEATH PUTREFACTION - this stage the sh is already spoiled fi  STAGES OF SPOILAGE Rigor Mortis Autolysis Bacterial Decomposition Lipid Oxidation *Known as RAB-L ORGANOLEPTIC CHANGES IN FISH Phase 1 Phase Phase3 (Fresh) (Not so fresh but still (Stale) acceptable) Eyes Bright, convex Flat Cloudy, sunken Skin Glossy with thin slime Lost gloss and cloudy slime Bleached with thin slime Gills Red or bright ppink with Dark red or partly bleached Bleached, dark brown, very clear slime slimy Scales Bright, Intact Few number are removed Can be easily removed esp. along the pectoral area even with the slightest touch Odor Fresh, clean, seaweedy Earthy neutral Objectionable Texture Firm, elastic No elasticity Very soft, spongy Flavour Sweet, meaty Neutral Sour, bitter, rancid, itchy Texture (cooked) Firm, juicy Less juicy, crumbly Dry, chewy pH 6.2-6.8 6.8-7.0 7.5-8.0 Water Test When dropped in a basin When dropped in a basin of When dropped in a basin of water, it sinks water, usually stays in the water, it floats middle